The present invention relates to transport apparatus for transporting flexible sheet-like articles, for example, sheets of paper, cards and envelopes.
Known machines for bundling letter or dispatch envelopes comprise intake equipment for inducting envelopes disposed in a stack. Such intake equipment includes a cylinder, which rotates in operation and which has suction openings for applying suction to successive envelopes, drawing individual envelopes from the base of the stack and, for example, transferring the envelopes to downstream transport equipment. At the point of each transfer, the suction openings are ventilated so that the envelope is released from the cylinder.
A known form of intake equipment has a cylinder with a shaft and two cylinder body portions, which are mounted on the shaft to be rotatable therewith and the circumferential surfaces of which incorporate a series of suction openings, which open into a suction channel extending along the rotational axis. The shaft is hollow and its interior connects the suction channels of the two cylinder body portions to a suction device via a control coupling. The control coupling comprises a first part fastened to a frame of the equipment to be non-rotatable relative thereto and a second part connected to the shaft to be rotatable therewith. The two parts have air passages with openings which, in a certain rotational position of the cylinder, face each other. In this rotational position, the cylinder applies suction to successive envelopes and entrains the envelopes in succession. The control coupling is also provided with a ventilation channel in order to ventilate the suction openings in another rotational position of the cylinder.
Present between the two cylinder body portions is a groove in which is arranged a separating device. The separating device is mounted on the frame to be non-rotatable relative thereto and is provided with a suction opening, which is located in the interior of the groove below the envelope stack. The suction opening of the separating device is connected via a duct with separate suction control couplings, which in turn are connected with the suction device. Each of these control couplings comprises a first part fastened to the frame to be non-rotatable relative thereto and a second part which is mounted on a separate shaft and which is rotated synchronously with the cylinder by a gear. This separate control coupling is constructed in such a manner that the suction opening of the separating device, in a particular rotational position of the cylinder, supplies suction to suck the lowermost envelope of the stack partially into the groove. Subsequently, this envelope is released by ventilation of the suction opening of the separating device so that it can be entrained by the cylinder. The separating device ensures that only one envelope is drawn away from the stack at a time.
In the known equipment, relatively long air paths are present between the two control couplings and the suction openings of the cylinder and separating device. In operation of the equipment, these air paths must be alternately partially evacuated and then ventilated. For this purpose, a relatively large quantity of air must be sucked away or let in. This entails the disadvantages that the maximum possible operating speed is relatively limited and a considerable amount of noise is generated. The noise is to a large extent caused by the substantial quantities of air which must be sucked away from or let into the air paths. In particular, ventilation generates noise like a report on the sudden inflow of air. Furthermore, the known intake equipment has the disadvantage that the control couplings require a considerable amount of space and thereby increase the overall size of the equipment.
Transport cylinders with suction openings are used not only for intake equipment, but also for other transport and deflection purposes. For example, in the specification of Swiss Patent Application No. 1 0847/78, there is described a cylinder, which serves to provide a deflector and which has a number of suction channels each provided with a plurality of suction openings opening at the circumferential surface of the cylinder. The suction channels open at one of the end faces of the cylinder. The cylinder is associated with a suction control coupling comprising a ring which is nonrotatably fastened to the frame and is co-axial with the cylinder. The end face of the ring facing the cylinder end face in which the suction channels open is provided with grooves extending along a circular arc and with a radial ventilation groove. In certain rotational positions of the cylinder, the suction channel openings in the end face of the cylinder communicate with the grooves in the ring of the control coupling, so that air is either sucked out of the suction channels or else the suction channels are ventilated.
This deflector is also only capable of operation at relatively low speeds. The grooves in the stationary ring of the control coupling and the openings of the suction channels at the end face of the cylinder extend for only a relatively short distance in radial direction because only a small space is available between the shaft and the outer rim of the cylinder. Accordingly, the flow cross-sectional area for air transition from the stationary ring of the control coupling to the cylinder is relatively small, with the result that the operating speed of the deflector is correspondingly limited to a relatively low value. This is particularly so because at least a part of the air in the cylinder itself must traverse a relatively long path due to the fact that all the air is sucked away or flows in at one end face of the cylinder and thus in part must flow through almost the entire length of the cylinder.